1. Field of the Invention
This invention relates to an adhesively correctable film typewiter ribbon having delayed alteration resistance which is especially adapted for use in conjunction with an adhesive typewriter ribbon of the type that is used to lift off a type indicia of non-absorbent and non-wetting ink compositions. The delayed alteration typewriter ribbon is especially adapted for use with a typewriter such as the Correcting Selectric typewriter manufactured by International Business Machine Corporation. This invention eliminates adhesive lift off of a typewritten character from the typing bond after a predetermined time duration.
2. Description of the Prior Art
Various formulations for adhesive correctable film typewriter ribbons have been heretofore been constructed. Such ribbons are capable of being utilized to imprint a letter on a piece of typing bond and are susceptible to adhesive removal without damage to the bond. These prior art ribbons are made of hard, film forming resins which are modified through the addition of additives which imbrittle the film and make the resin adherent to the imaging surface while not penetrating into the fibers of the paper that is typed upon.
Prior art film ribbons utilize non-absorbent ink compositions of transfer materials, which do not wet or dye the paper onto which indicia are placed. Accordingly, this makes possible the use of adhesive materials for correcting an error by removing the undesired typed character with an adhesive tape carried by the typewriter. Furthermore, adhesive lift off removal of typewritten characters made by prior art ribbons is possible for substantially an indefinite period of time. Known correctable typewriter ribbons do not wet the typing bond after being deposited thereon by mechanical force and accordingly adhesive removal was possible even after the passage of long periods of time as the character did not penetrate into the fibers of the paper.
In the past, there have been various attempts to increase the attachment of a lift off removable typewritten character as time passes, however, these prior art ribbons do not leave a visible image after being adhesively removed after long periods of time have passed.
It is further known to provide a typewriter with a ribbon that incorporates ink of the type that is capable of penetrating into the paper fibers and staining or permanently dyeing the paper upon being printed thereon. However, adhesive removal of such an indicia was not possible at any time, and the fibers of the paper had to be physically removed from the surface of the paper to remove the image.
The difficulty involved with known typewriter ribbons is that none have been found to be readily adhesively correctable shortly after being typed, and yet exhibiting a delayed alteration resistance at a later time.